CN1004454B

CN1004454B - High-pressure sodium discharge lamp

Info

Publication number: CN1004454B
Application number: CN86104354.5A
Authority: CN
Inventors: 雅各布斯·马里纳斯·玛丽亚·克拉森斯; 杰拉达斯·马里纳斯·约瑟夫斯·弗朗; 西斯库斯·卢杰克斯
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1985-06-05
Filing date: 1986-06-02
Publication date: 1989-06-07
Also published as: HUT41158A; US4755710A; DE3669235D1; JPS61201262U; HU193859B; EP0204382B1; CN86104354A; EP0204382A1; JPH0615393Y2

Abstract

The invention relates to a high-pressure sodium discharge lamp which is used in conjunction with an external starter or an internal starter without glow discharge. The lamp has an outer bulb provided with a base and an enclosed empty space. In which a discharge tube is mounted. According to the invention, a closed gas reservoir is arranged in the space enclosed by the outer bulb, the walls of the reservoir containing essentially glass components. The box is at least stored with helium. This results in a lamp voltage increase which is considerably reduced during the life of the lamp.

Description

High-pressure sodium discharge lamp

The invention relates to a high-pressure sodium discharge lamp which is used in conjunction with an outer starter or an inner starter without glow discharge. The lamp has an outer bulb provided with a lamp base and a closed vacuum space in which a discharge vessel is arranged.

Such lamps as described above are known, for example, from the European patent Specification 0132886 (PHN 10746). Such lamps are often used in public lighting because of their high luminous efficiency, long life and pleasant color of emitted visible light.

The discharge vessel of the lamp is usually made of metal oxide ceramics, for example polycrystalline densely sintered aluminum oxide or single crystal sapphire. The discharge vessel is filled with a sodium amalgam composition, which is typically provided in excess of its formulation. In lamps with an excess of ingredients, the vapor pressure in the operating state of the lamp is dependent on the temperature of the excess condensate, and the temperature of the coldest zone is generally known.

High-pressure sodium discharge lamps require a high starting voltage, so that in practice the lamp is used in conjunction with a starter. The lamp according to the invention is used in connection with an outer starter or an inner starter without glow discharge. The term "outer starter" in this specification means that the starter is mounted outside the vacuum outer bulb, unlike a lamp in which the starter is mounted inside the vacuum outer bulb. In principle, the outer starter may be mounted in any position with respect to the lamp, for example in a lamp-mounted luminaire or on a pillar mounted luminaire, while it is more desirable to mount the starter in the lamp base.

In practice it has been found that the lamp voltage during the life of the known lamp appears to increase after an initial phase of decrease. For lamps using an ac power supply, an increase in the restart voltage is caused each time the supply voltage changes polarity. The increasing lamp voltage and the restart voltage cause the lamp to extinguish and end its life. In general, a decrease in lamp voltage results in a decrease in lamp power and lamp brightness.

It is an object of the invention to provide a method of reducing the increasing lamp voltage during the lifetime of a lamp. It is a further object of the invention to extend the life of the lamp and to minimize the variation of the lamp efficiency during life.

According to the invention, in order to achieve the above-mentioned objects, a sealed gas container, at least helium-containing, is arranged in the vacuum envelope of a lamp of the type described in the opening paragraph, the container wall of which container essentially comprises a glass composition. The term "glass composition" is understood to mean either one of the materials SiO ₂、B₂O₃ and P ₂O₅, or a mixture thereof.

It was found that the lamp according to the invention has a significantly reduced lamp voltage increase compared to the known lamp. Since the lamp life is limited by an increase in lamp voltage, the lamp life according to the invention is increased and its efficiency is similar to that of the known lamp.

The present invention is described below. It is known that during the lifetime of the lamp, the thermal control changes due to the effect of blackening at both ends of the discharge vessel, resulting in an increase of the coldest spot temperature. An increase in the coldest region temperature in turn leads to an increase in the lamp voltage.

Among the methods of increasing heat dissipation of the discharge tube to lower the coldest region temperature, a method of affecting thermal control is to reduce the vacuum level around the discharge tube, which is well known. For example, usupS3932781 (PHN 4840) is known. In this case, heat dissipation is achieved by means of thermal conduction from the surface of the discharge vessel. However, in general, this affects the lamp efficiency. The effect that is experienced in this known method of influencing the thermal control is the same as the effect that the lamp is subjected to during the entire lifetime. Viewed from another aspect, the lamp voltage increases with time.

Helium diffuses out through quartz and glass under the influence of temperature, as is well known. It has surprisingly been found that a closed gas-storage vessel containing helium gas and having a vessel wall comprising mainly glass components, in which vessel the helium gas diffuses into the vacuum space at such temperatures when the closed gas-storage vessel is installed in a vacuum envelope under operating conditions of a high-pressure sodium discharge lamp, that the increase in lamp voltage is significantly reduced. Although the lamp voltage may decrease somewhat faster initially due to the diffusion of helium, it was found that the effect on the lamp efficiency was not great.

Preferably, the closed gas storage box is arranged at one end close to the discharge tube. This provides the advantage that the emitted visible light is minimally blocked by the closed air reservoir and a sufficiently high temperature is obtained.

In a preferred embodiment of the lamp of the invention, the wall of the sealed gas reservoir contains a molar fraction of glass constituents of 65 to 90. At molar fractions greater than 90, the actual helium diffusion rate increases significantly and counteracts the effect of the decrease in lamp voltage at the beginning, compared to the effect of the increase in lamp voltage. This results in a considerable reduction of the lamp efficiency at the beginning, which is not satisfactory.

When the molar fraction is less than 65, the diffusion rate of helium is so low that the increasing lamp voltage can only be effectively compensated by the large surface of the sealed gas storage box.

In a preferred embodiment, the airtight container satisfies the following relationship:

2.5×10⁵≤0/V·d≤10⁶

Wherein O is the outer surface area of the sealed gas storage box which can permeate helium, and m ²;

V is the volume of the closed gas storage box, m ³;

d is the thickness of the wall of the airtight gas storage box and m.

If the relationship 0/Vd is greater than 10 ⁶, it is found that helium diffuses very rapidly through the wall of the sealed gas storage tank and when operated for 2000 hours, the lamp efficiency is reduced by 10% or more compared to the same time as the known lamp.

The relationship is disadvantageous in that the value is less than 2.5X10 ⁵, the diffusion of helium is so small that the effect of heat dissipation and the suppression of the increase in lamp voltage are negligible unless special measures are taken, such as a high helium filling pressure or additional heating of the closed gas storage tank.

In another preferred embodiment, the lamp satisfies the following relationship:

Wherein V is the volume of the closed gas storage box, and m ³;

V _b is the volume of the outer bulb, m ³;

P is the pressure of helium filled in the sealed gas storage box at 300K.

If the value of the relation is greater than 94, the diffusion rate of helium is so high that it leads to a significant decrease in lamp efficiency at the beginning, which must be avoided. At values of the relation less than 24, special measures, such as increasing heating or thinning the wall thickness of the cartridge, have proved necessary in order to effectively reduce the increasing lamp voltage.

The lamp according to the invention will now be described in detail by way of example with reference to the accompanying drawings.

The outer bulb 1 of the high-pressure sodium discharge lamp is provided with a lamp cap 2 and encloses a vacuum space 13 in which a discharge vessel 3 is arranged. Electrodes 4, 5 are mounted at both ends thereof, respectively. In the operating state of the lamp a discharge is generated between the electrodes 4, 5. The electrode 4 is connected to a hard power lead 7 by a metal strap 6. This power supply lead 7 leads to the connection of the lamp cap 2. The electrode 5 is also connected to a hard power lead 9 via a metal strap 8. The power supply lead 9 leads to another connection of the lamp cap 2.

Reference numeral 10 denotes a closed gas storage box having a glass wall 10a, which is positioned by means of

wires

11, 12 fixed to the power supply wire 9. A single wire may also be used to secure the airtight gas storage cassette. The positioning wires may also be fixed to the power supply wires 7.

A high-pressure sodium discharge lamp designed to dissipate 70W of power and used at a supply voltage of 220V, 50HZ is actually connected to an external starter. The volume V _b of the vacuum space 13 enclosed by the outer bulb 1 was 260×10 ^-6m³, the volume V of the enclosed gas storage box 10 was 1.7×10 ^-6m³, the helium-permeable surface area was 7.9×10 ^-4m², and the thickness of the glass box wall 10a was 0.9mm. The helium pressure charged at 300K in the closed gas storage box 10 was 7 kpa. Thus, the value of the relation 0/V.d for the sealed gas storage case was 5.1X10 ⁵. The value of the lamp relation 0/V _b P is 47. The wall 10a of the closed gas storage box is composed of glass whose composition is SiO ₂ and whose molar fraction is 77. During lamp operation, the temperature of the sealed gas storage cartridge wall is 180 ℃. The lamp voltage and lamp efficiency of said lamp were measured several times during the lifetime, which is also applicable to prior art lamps in corresponding proportions, the results of which are presented in the table below. The lamp voltage value and the lamp efficiency value are expressed in% with respect to the value at the time of operation for 100 hours of life. In addition, similar results for lamps designed to dissipate 150W and 400W are also listed.

Watch (watch)

As can be seen from the table, the 70W lamp according to the invention has a lamp voltage increase of 20% less than the known lamp after 10000 hours of use. Either of these lamps has not yet reached the end of life. From the course of the increase in lamp voltage it can be deduced that the lifetime of the lamp according to the invention will be 25% longer than the lifetime of the known lamp.

In a 70W lamp according to the invention, the helium pressure in the vacuum envelope is 0 Pa after 100 hours of operation and 3.6 Pa after 10000 hours of operation. The helium pressure in the sealed gas storage box is 7 kilopascals after 100 hours of operation and is reduced to 6.2 kilopascals after 10000 hours of operation under 300K.

Claims

1. A high-pressure sodium discharge lamp used in conjunction with an external starter or an internal starter without glow discharge, comprising an outer bulb equipped with a lamp cap and an enclosed vacuum space in which a discharge tube is mounted, characterized in that a sealed gas container containing at least helium is mounted in the enclosed space of the outer bulb, the container walls of which mainly consist of glass.

2. A lamp as claimed in Claim 1, characterized in that the closed gas container is mounted near the end of the discharge tube.

3. The lamp according to claim 1, wherein the glass component of the wall of the airtight gas storage box has a gram mole fraction of 65-90.

4. A lamp according to any one of the preceding claims, characterized in that the sealed gas container satisfies the following relationship:

2.5×10 ⁵ ≤0/Vd≤10 ⁶ ,

Where: O is the surface area of the sealed gas box that can be permeated with helium, m ² ;

V is the volume of the sealed gas storage box, m ³ ;

d is the thickness of the wall of the sealed gas storage box, m.

5. A lamp according to any one of the preceding claims, characterised in that the lamp satisfies the following relationship:

Where: V is the volume of the closed gas box, m ³ ;

V _b is the volume of the outer bulb, m ³ ;

P is the pressure of helium in a sealed gas storage box at 300K, Pa.